Known prior proposed machinery is disclosed in the following listed U.S. Pat. Nos.:
______________________________________ 3,657,044 Singer 4,308,005 Zundel 3,767,501 Thiel 4,383,954 Rider, Jr. 4,289,469 Keim 4,427,476 Beck et al 4,302,415 Lake ______________________________________
Both the patents to Thiel U.S. Pat. No. 3,767,501 and Beck et al U.S. Pat. No. 4,427,476, which are believed the only two worthy of specific mention, disclose methods for forming double-walled plastic articles, such as cups which are to have thermal insulating properties, and comprise an outer jacket and an inner liner sized to fit within the jacket. In the Thiel patent, a multiplicity of jackets and liners are formed simultaneously in a single thermoplastic, synthetic web, or jackets and liners are separately formed in different webs at separate molding stations. Later, the webs containing the batches of jackets and liners are trimmed to separate the articles formed from the webs, and the trimmed jackets and liners are individually paired, internested, and joined by way of heat welding the peripheral area surrounding the cup mouths.
In the Beck et al patent, a pair of webs are fed through heating means to raise the temperature of the material to a thermoforming and orientation temperature and then move to a mold station wherein a mold assembly functions alternately to form a plurality of containers in one web, while permitting the stripping of another web from the molding apparatus. In other words, while one web is stationarily clamped between the closed units of one of the mold unit sets and is being molded, the other web is being advanced to remove the newly formed articles from the other of the mold unit sets, and move a heated, deformable new section into molding position. Thereafter the container cup and barrier cup are paired and internested, and the portions of the webs surrounding the mouths of the internested parts of the container are suitably bonded together, and then may be blanked from the webs to provide a double-walled container.